cst microwave waveguide port

I am beginner in electromagnetic simulation I am using CST microwave. I want to designe a monoploe antenna. I used a solid cylinder for rod placed a insulator around it in bottom then a ground plane around it with the same material as of rod.I used insert bolean for combining insulator, groun and roung. and selected face of insulator (circle) and made it a wave guide port but when runs error is calculation domain is PEC check your background, but i checked background nothing is wrong with it, someone help me how shld attach waveguide port , shld it also be connected with ground how the waveguide port is used.
thanks in advance

If you have checked Solve/Background Material? You should use normal instead of PEC for the materials.

check this
http://www.jedi.net/%7Ejustin/CST/monopole.html